There are a plethora of indoor air purification devices currently on the market; however, these devices (e.g. mechanical filters, electronic air cleaners, ion generators, etc.) focus on the removal of airborne particulates. The conceptual indoor air purification system has been designed to address the recent air quality problems associated with gaseous chemical contamination which has become more of a problem in recent years due in part to inadequate ventilation, chemical pollutants from indoor sources and chemical contaminants from outdoor sources. New "tight" buildings and increased energy costs have led to a significant reduction in the amount of outdoor air provided for ventilation which results in the accumulation of indoor air pollutants.
It is well documented that volatile organic compounds (e.g. formaldehyde, etc.) are released from adhesives, pesticides, cleaning agents etc. The so called "Sick Building Syndrome" is commonly found in new buildings where carpet adhesives are still emitting harmful compounds. Carbon monoxide emissions from fireplaces, gas stoves, space heaters, and faulty furnaces (and smoking) are considered a significant problem in the northern climates and many major cities are passing ordinances requiring carbon monoxide detectors in single and multifamily homes. Ventilation with the polluted outdoor air in major metropolitan areas (e.g. motor-vehicle emissions, and smog (ozone) reduces the quality of indoor air.
Purification of air that is polluted with the above mentioned types of gaseous chemical contaminates can be accomplished through the use of adsorbents or catalysts. Effective clean-up of indoor air can require several beds of different types of adsorbents that will have capacity limitations. In contrast, catalysts can affect the continuous removal/destruction of a wide range of malodorous/harmful organic compounds, carbon monoxide, and ozone. However, standard air purification catalysts often operate at relatively high temperatures, which has discouraged their use in indoor air purification.
Sick Building Syndrome (SBS) and other related air quality issues have promoted a series of recent studies by the EPA and other agencies which suggest that the indoor air purification market can be immense. For example, the adverse effect of poor office air quality on employee productivity was estimated to cost industry "in the tens of billions of dollars per year" (EPA Report to Congress on Indoor Air Quality, 1989).
Competitive units do not use catalyst technology for control of gaseous chemical contaminates (they typically are particulate removal devices). U.S. Pat. No. 4,138,220 (1979) to Davies, et. al. discloses forcing air through a heat exchanger to preheat the contaminant-laden air, preheating it with electrical heaters to a reaction temperature in the range of 357.degree.-475.degree. F., passing the heated air across catalytic units, and discharging the converted air through a heat-exchanger. U.S. Pat. No. 5,447,693 (1995) to Ohta et al. uses the heat exchanger fins of an air conditioner that are coated with a catalyst. In the cool mode, contaminants adsorb to the coated fin; in the hot mode, they react and desorb. U.S. Pat. No. 5,252,299 (1993), to Retallick does not use forced air but instead uses two strips to form counter current spiral paths around a heated converter.
In contrast, our application is the commercial or residential setting, where the application includes, but is not limited to, odor-causing compounds such as sulfur, oxygen, or nitrogen containing compounds, and carbon monoxide, and ozone. Our system may operate over a large temperature range depending on how it is implemented (recycle or once-through mode).
The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts, all as detailed below, and the scope of the invention will be indicated in the claims.